What is largest heat bed and source

[Tachout]

I am wondering what the largest heat bed is and is there a source out there for one? Right now my printer has a 8"X8" bed (Roughly) I want to build one very similar to mine that has a 2'-0"X3'-0" printable area. I know it is a big step, but want to be able to print anything I can draft and then put to scale on a D size print, and be able to print it in one step rather than break the model, then print, then have to assemble the pieces.

Anyone know a source for one that large or larger that I could work from... Even if it is a few pieces of bed, and have to have its own controller to control all the beds. (I am not smart enough on that so that is going to take some help.

Mark

[old man emu]

I'd say that a 600 x 900 mm print bed is something that you are going to have to make yourself. This is not as hard as it sounds. The biggest problem is sourcing resistance wire fine enough so that you aren't using heaps of Watts when heating. You will need to know the resistance per metre of the wire to calculate the power per metre (P = V^2/R)

If you can source the resistance wire, then all you need do is get a sheet of aluminium (aluminum to Yanks) and lay down a layer or two of Kapon tape. Lay down your resistance wire in a coiled pattern. Cover the coil with more Kapon tape, or a coating of heat-proof fibreglass resin.

Old Man Emu

EDIT: I have a better idea. Instead of Kapon tape, apply a thick coating of ABS slurry to your sheet of metal. Then lay down the resistance wire and cover it with another layer of ABS slurry. Since the print bead is not going to be heated much above 120 C, the slurry will not melt.

For your calculations, the resistance per metre of Nichrome wire is 5.4 ohms/metre for AWG24 (0.020") and 2.16 ohms/metre for AWG 30 (0.32")

OME

[printbus]

In post 15 of this thread in the reprap format forum, user nka provides a link to a heatbed supplier that can do custom sizes. Try asking them.

Have you though about how much power consumption and heat dissipation is involved here? I think the typical 8" x 8" heater is 130 watts, or 300w per square foot. An equivalent 2' x 3' heat bed would be 1800 watts, or about the same as a large toaster or toaster oven. At 12v, you're having to control a very substantial 165 amps of current to provide this amount of power. The supplier nka points out can do heaters for 120v or 230v, which would get the amps down to something easier to control but...

Of course, maybe 300w per square foot isn't required. But then you're getting into variables in how long the bed takes to heat and how it maintains temperature.